Rockwell Automation T8444 Trusted TMR Pulse Generator and Monitoring Module - Manual (Page 39)

Trusted
TM
Module T8444
Issue 09 Apr 10 PD-T8444 39
6.9. Detection of a short/ long pulse
Deviation of pulse length is detected. This is performed by a window detector should a pulse
feedback start late or complete early a fault is indicated. The fault detection window is
15mS.
The window for short and long pulse width is 15mS. Under normal operation if the input is removed
when an AC phase had just started, the SCR would continue to conduct until the AC phase crossed
the 0V line again. Worst case could be close to 8ms.
6.10. Analogue Feedback out of limits
No specific high or low limits are set. Failure of the transmitter is detected by the detection of a
missing or extra pulse, so no thresholding other than the detection of the presence of a pulse and
missed firings is needed.
6.11. Motor Voltage Monitoring
The Average level of the feedback pulse provides a measure of the voltage being applied to the motor.
This level is sampled once per pulse to determine that it is within specification.
8mS
Output
Off
Normal Waveform
Input Removed
Acceptable
window Acceptable
Window
Initiating Pulse
Feedback Pulse